Study on the Relationship of 25-hydroxyvitamin D and Intact Parathyroid Hormone in Chinese Young Adults

Abstract Background : Vitamin D plays an important role in bone health and other diseases, however, there is no consensus over the optimal serum 25-hydroxyvitamin D (25(OH)D) concentration. Many studies defined a level of serum 25(OH)D at which serum intact parathyroid hormone (iPTH) levels decreased and reached a plateau might be the optimal status for vitamin D sufficiency. This study was performed to study the relationship between 25(OH)D concentration and intact parathyroid hormone (iPTH) concentration in the Chinese non-clinical young population aged 18-44y. Methods : The serum samples of young adults aged 18-44 years old were selected from the established serum bank of Chinese Chronic Diseases and Nutrition Survey (CCDNS, 2015-2018). The serum 25(OH)D concentration was determined by high performance liquid chromatography tandem mass spectrometer, and the iPTH was determined by electronic chemiluminescence method. The relationship of 25(OH)D and iPTH were analyzed by partial correlation analysis, and the threshold of 25(OH)D was analyzed by locally weighted scatter plot smoothing method after adjusting the iPTH by age, season of blood draw, BMI, waist, sex and latitude. Results : 623 serum samples (293 male, 330 female) of 25(OH)D concentration and iPTH concentration were analyzed. Significant higher 25(OH)D concentration was found in male than female. And the samples from the southern China had higher 25(OH)D concentration than those from the northern China. Samples from autumn had higher 25(OH)D concentration than those from spring and winter. The inversely relationship between 25(OH)D concentration and iPTH concentration was observed when the 25(OH)D was below 17.6 ng/mL for both sexes. The threshold for male was 16.2 ng/mL and it was 25.6 ng/mL for female. Conclusions : The threshold and the relationship between 25(OH)D and iPTH differs by sex among Chinese young adults aged 18-44y. Further study is needed to evaluate the sex-specific ranges of optimal vitamin D. Trial registration : Not applicable.